Hi, mi recent experiments with multi-threaded python wrappers for QGIS server showed a critical flaw in my original implementation of the server plugins.
First, I want to stress that this is not a problem in FCGI server implementation but only if the server is used directly from python in a multi threaded server implementation. The problem is that the server interface that exposes the request handler is a static property of the interface, that is changed on every request. This means that there is a race condition in setting/accessing the handler from a plugin filter, and that a plugin filter might access to the handler for a wrong request. The solution is to pass the request handler (or the request and/or response objects depending on the filter) to the plugin filters and leave the interface for static properties only. This would be a big API change for the server interface and filters and I'm not sure we have time/resources to do that now. As an alternative we could simply document the issue and change the testing code to create a new server instance to server every request (to be verified, and with consitent performance degradation). What's your opinion about this issue? BTW, tomorrow I'll file a ticket for this problem. -- Alessandro Pasotti w3: www.itopen.it
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